Approximately 2,041 dams in 148 watershed projects have been constructed in Texas. The programs under which these dams were constructed include PL 83-566, PL 78-534, Pilot Watershed Projects, and Resource Conservation and Development (RC&D) . A typical candidate site for rehabilitation was constructed between the late 1950’s to the middle 1960’s, with the majority of the dams constructed in the central part of the state, now referred to as the Interstate 35 corridor. The Interstate 35 corridor reaches from the Dallas-Fort Worth metroplex south to San Antonio. When the projects were planned the majority of this area was in a rural setting. Conversion from agricultural to urban land use has taken place and is intensifying. Many dams originally constructed as low hazard are now classified as high hazard, or will soon be high hazard as a result of downstream urbanization.
Dams are classified according to their potential to impact human lives and public infrastructure should a failure occur. Failure of a low hazard dam has the potential to cause damage to agricultural land, farm buildings, and rural roads. Failure of a significant hazard dam has the potential to damage minor state roads and utilities. Failure of a high hazard dam has the potential to cause significant damage to urban structures, main highways, and utilities, as well as potential to cause loss of life. Many high hazard dams were originally designed for a rural setting according to low hazard criteria. These dams must now be upgraded to meet high hazard criteria.
The typical dam has a drainage area of 600 to 3000 acres, a height of 25 to 40 feet, and 500 to 1500 acre-feet of detention storage. Depending on the amount and type of urban development adjacent to these dams and condition of the embankment and structural components, rehabilitation may cost from $700,000 to $2,000,000. Rehabilitation costs are shared 65 percent federal and 35 percent local watershed sponsors.